Charlie Kirk was one of the most high-profile conservative activists and media personalities in the US and a trusted ally of President Donald Trump.

Kirk, 31, who the president said died after a shooting at a Utah college on Wednesday, was known for holding open-air debates on campuses across the country.

In 2012, at the age of 18, he co-founded Turning Point USA (TPUSA), a student organisation that aims to spread conservative ideals at liberal-leaning US colleges.

His social media and eponymous daily podcast often shared clips of him debating with students about issues such as transgender identity, climate change, faith and family values.

The son of an architect who grew up in the well-to-do Chicago suburb of Prospect Heights, Kirk attended a community college near Chicago before dropping out to devote himself to political activism. He applied unsuccessfully for West Point, the elite US military academy.

Kirk often referred tongue-in-cheek to his lack of a college degree when engaging in debates with students and academics on esoteric topics such as post-modernism.

His role in TPUSA took off after President Barack Obama was re-elected in 2012.

Kirk toured the country speaking at Republican events, many popular with members of the ultra-conservative Tea Party movement. TPUSA now has chapters in more than 850 colleges.

An avid public speaker, Kirk addressed the Oxford Union earlier this year, and wrote a 2020 best-seller The Maga Doctrine.

TPUSA played a key role in the get-out-the-vote effort for Trump and other Republican candidates in last year’s election. The millennial was widely credited with helping to register tens of thousands of new voters and flipping Arizona for Trump.

Kirk attended Trump’s inauguration in January in Washington DC, and has been a regular visitor at the White House during both Trump terms in office.

The president and his aides valued Kirk’s political antenna for the grassroots of the Make America Great Again movement.

He’s spoken at Republican conventions and last year Donald Trump repaid the favour by giving a big speech at a Turning Point conference in Arizona.

Earlier this year, he travelled with Trump’s son, Donald Trump Jr, to Greenland, as the then-incoming president was arguing that the US should own the Arctic territory.

Kirk’s evangelical Christian religion and family – he married a former Miss Arizona, with whom he had two children – were front and centre in his politics, and he was seen as both the future of conservative activism and a highly polarising figure.

Perhaps the biggest tribute to his contribution to Republican politics came from Trump himself in a clip played at the beginning of Kirk’s podcast.

The president says: “I want to thank Charlie, he’s an incredible guy, his spirit, his love of this country, he’s done an amazing job building one of the most powerful youth organisations ever created.”

Kirk discussed numerous political and social at his events and on his podcasts – gun control is one of them.